Flap belt electroplating apparatus

ABSTRACT

A pair of flexible support members positioned exterior of an parallel to a plating zone defined by the cathodic workpiece and a conforming, closely-spaced pressure member are utilized to move a multiplicity of partially-overlapping porous, resilient hard particle- carrying activator sheet materials through such plating zone in contact with the surfaces of the workpiece receiving the plate throughout the period of imposed current flow.

A ril 23, 1974 H, ROWE 3,806,441

FLAP BELT ELECTROPLATING APPARATUS Filed Sept. 11, 1972 2 SheetsSheet 1April 23, 1974 c ROWE 3,806,441

FLAP BELT ELECTROPLATING APPARATUS Filed Sept. 11, 1972 2 Sheets-Sheet 2EMQWWM v a M M-"WW United States Patent Office 3,806,441 Patented Apr.23, 1974 3,806,441 FLAP BELT ELECTROPLATENG APPARATUS Carl H. Rowe,Scotia, N.Y., assignor to Norton Company, Troy, N.Y. Filed Sept. 11,1972, Ser. No. 288,040 Int. Cl. 301k 3/ C23b 5/00 U.S. Cl. 204-224 RClaims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION The presentapparatus is used in the field of electrodeposition and morespecifically as a means to practice the process disclosed and claimed inU.S. Letters Patent No. 3,619,384, issued on Nov. 9, 1971 to SteveEisner and entitled Electrodeposition. Such process is hereinafterreferred to as the N-E-T I" process for convenience of description. Inparticular, the present apparatus is designed to permit the practice ofsuch process on the plating of interior and/or exterior surfaces ofworkpieces having curved or contoured configurations such that any pointon the surface to be plated a straight line can be drawn from one sideto the other on such surface and remain in a single plane. Typicalexamples of such workpieces are cylinders or an epi-trichoid such as theinterior of the housing of the rotary combustion engine commonlyidentified as the Wankel engine.

PRIOR ART The aforesaid process patent, No. 3,619,384, and a series ofrelated patents issued on the same date to the same patentee, Nos.3,619,401, 3,619,383 and 3,619,400 are believed to be the closest priorart. A copending application of Steve Eisner, Ser. No. 102,287 entitledVibratory Process and filed on Dec. 29, 1970, now U.S. Pat. No.3,699,014 illustrates another approach to the problem met by theapparatus of the present invention.

SUMMARY OF THE INVENTION In the N-E-T I process, a plurality of small,hard activating particles supported in fixed relationship to one anotheron at least the surface of a porous, flexible, resilient, supportingmatrix, are moved over the surface of an electrodeposit as it formsthroughout the period of electrodeposition. The repetitive particlecontacts at very short time intervals mechanically activate the depositsurface, drastically increasing the rate at which metal in a sound,coherent form can be deposited on such surface. The process either takesplace below the surface of the electrolyte or electrolyte is floodedinto the plating zone at a high rate to provide the requisite supply ofmetal ions.

Apparatus for practicing this process is disclosed and claimed in theaforementioned U.S. Letters Patent No. 3,619,401 while apparatusspecific to depositing plate on flat strip is disclosed and claimed inthe aforementioned U.S. Letters Patent No. 3,619,383. Both of theseillustrate the process as applied to flat stock such as strip or tomildly-contoured items such as rolls. The aforementioned copendingapplication, Ser. No. 102,287 illustrates what can be termed shapedwheels as one way of applying the particle-carrying activator materialto two-dimensionally contoured shapes such as bumpers or the like. Thepresent invention is an improved apparatus for operating ontwo-dimensionally curved surfaces and essentially consists of a pair ofspaced, flexible support members maintained essentially parallel withone another at any given point in the length of such members. Disposedbetween such flexible support members and affixed thereto by engagementwith generally rigid cross-connecting members extending between theflexible members are a number of sheets or flaps made of suitableactivating materials. As described in the aforementioned patents, suchactivator materials are preferably porous, compressible and resilientwebs, usually formed from fibers chemically resistant to the platingsolutions with which the material is to be used and anchored one to theother in a nonwoven form. Woven, non-porous materials can be used asdescribed in such patents but are not preferred. Afiixed to at least thework-contacting surface of such webs and anchored thereto by a suitablechemically-resistant adhesive in spaced relationship one to another area plurality of small, hard activating particles, usually, but notnecessarily, abrasive grains. The description of such materials isbelieved sufliciently complete above but the disclosure thereofcontained in the aforementioned U.S. Letters Patent are incorporatedherein by reference for sake of completeness. Generally such activatormaterials have been illustrated in the foregoing patents in the form ofbelts, discs, wheels or the like capable of moving over the surfacebeing plated or in the form of static sheets over which the surface tobe plated is moved as more specifically described and claimed in thecopending application Ser. No. 256,884 of Steve Eisner, entitled PlatingApparatus and filed on May 25, 1972. Here, as aforesaid, such materialis provided in the form of a plurality of sheets, usually rectangular inshape, which are interposed between and supported by the parallel,flexible spaced support members. This structure is inserted into aplating system where the interior or exterior surface of atwo-dimensionally curved workpiece is to be plated. As part of theapparatus, a pressure-plate closely conforming to the contours to beplated of the workpiece is provided and positioned in close proximity tosuch contours on the workpiece. The workpiece and this pressure platedefine the plating zone and usually and preferably, the pressure plateserves double-duty as the inert anode in the system. In all cases, suchpressure plate is perforated at frequent intervals over its entiresurface to permit ready electrolyte flow therethrough. Where the plateis made of plastic or the like, anodes are placed adjacent itsperforated outer surface. The flaps or sheets of activator material areinterposed in the plating zone defined by the workpiece and the pressureplate with the flexible support members outside such zone and on eachside thereof. For purposes of convenience, such positioning of thesupport members relative to the plating zone is generally hereinafterreferred to as being outboard of such zone. The flaps of material arepreferably so spaced that the end of one flap overlaps the start of thenext when the flaps are confined within the plating zone. The ouboardsupport members run parallel with the contours of the plating zone andwith each other. Means are provided to drive these outboard supportmembers, which are preferably and usually in the form of endless loops,so as to pull the overlapping flaps through the plating zone defined bythe workpiece surface and the conforming pressure plate. As isillustrated in the drawings discussed below, coverage of quite complexcontours can easilv be achieved with this annaratus arrangement.

DRAWINGS FIG. 1 is a schematic illustration of one form of the supportmembers and associated cross-connecting members here shown without theactivator materials for purposes of clarity in illustration.

FIG. 2 is a cross-sectional view long the line 2--2 of FIG. 1 with theactivator flaps inserted.

FIG. 3 illustrates schematically a different form of support member andconnecting member arranged according to the present invention (and againshown without the activator flaps for clarity).

FIG. 4 is a schematic end view of a part set up in a plating tank forinternal surface plating as is shown in more detail in FIG. 5.

FIG. 5 is a cross-sectional view taken on line 55 of FIG. 4 of acontoured workpiece set up for interior surface plating in accordancewith the present invention.

FIG. 6 is a schematic illustration of the plating of a portion of theexterior surface of a rotating cylinder with apparatus of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings,FIGS. 1-3 illustrate several types of support structures which may beused as components of the present apparatus. With reference to FIG. 1,the support structure 10 consists of a pair of parallel, spaced,flexible support members 11 (here shown as hollow plastic tubing)connected to each other by sets of cross-connecting members 12, each ofwhich has a bent end 13 which, when inserted into holes in supportmembers 11, prevents the accidental dislodgment of member 12 therefrom.Spring clips 14 are slipped over the ends of each set ofcross-connecting members 12 to urge them toward each other to providefor positive locking in place of the sheets or flaps of activatormaterial held between the cross-members 12 in use as shown in FIG. 2.

In FIG. 2, the support structure 10 of FIG. 1 is shown with theactivator flaps 15 in place on cross-connecting members 12. Asillustrated, each activator section 15 is inserted between therespective sets of pins or cross-members 12 so that the upper end 18(which will contact the workpiece in usage) of such activator flap 15overlaps or essentially overlaps the next section 15 forming anessentially continuous surface of activator material. These ends may betapered if desired to provide better uniformity of contact butgenerally, due to the resilient nature of the activator material 16,such tapering is not necessary. As shown, at least the outer surface ofeach flap 15 supports a plurality of small, hard, spaced, activatingparticles 17 secured thereto by a suitable adhesive (not shown). Inoperation, all activating units are moved in the direction of the closedend of the flaps as indicated by the arrow.

FIG. 3 illustrates a schematic view of a slightly different type ofsupport structure. Here, a pair of fiat, flexible plastic strips are theparallel support members, each containing a continuous line of recessedopenings 31 designed to mate with drive teeth on the driving mechanism(not shown). The cross-connecting member 32 here is a single pin 33 foreach flap having a cut-out central portion 34 through which the flapmember is inserted. Each end of pin 33 is also cut out or notched asshown at 35 to allow the pin 33 to fit over the fiat support members 30.A rivet 36 fastens the split ends of pin 33 to the support members 30.

FIGS. 4 and 5 show apparatus of the present invention set up in aplating tank to plate the interior surfaces of a rotary enginecombustion chamber. The workpiece 40 is shown in FIG. 4 immersed in theplating electrolyte 41. Suitable electrical connections make at leastthe interior surfaces of workpiece 40 cathodic. The parallel, flexiblesupport members 42 are shown outboard of workpiece 40 with thecross-connecting members 43 extending through from one side to the otherof said workpiece 40. The support members are driven over drive pulleys44 mounted on shafts 45 by suitable means (not illustrated).

In FIG. 5, a cross section taken on line 5--5 of FIG. 4 illustrates theway the apparatus functions. Here, the

workpiece 40 immersed in the electrolyte 41 is shown as having anepi-trochoid shaped opening 50. Typical dimensions for such an openingare 11 inches in the vertical direction by 8 inches in the widthdirection by 3 inches in depth. While here illustrated as set up forplating a single unit in practice, multiples of 3 to 8 workpieces wouldusually be assembled and the plating carried out on all of these at thesame time using activator flaps of the appropriate width. The insidesurfaces 51 of the opening 50 are to be plated (usually with hardchrome). A conforming inert (lead) anode 52 is provided, closely spacedfrom such surfaces 51. A plurality of perforations 53 in the inert,conforming anode 52 permit electrolyte 41 to circulate freely throughthe anode and into the plating zone defined by such anode 52 and theworkpiece surfaces 51. Support structures such as 54 are usuallyrequired to maintain dimensional stability for anodes of this kind butcan be varied or dispensed with as desired. As shown, a plurality offlaps 55 of activator material such as has been described above arefastened to the connecting members 43. Rotation of the outboard supportmembers 42 (see FIG. 4) in the direction shown by the arrows on FIG. 5causes the hard particles carried by flaps 55 to activate the surfaces51 producing increased deposition rates in accordance with the N-E-T Iprocess.

FIG. 6 schematically illustrates a modified version of the apparatushere used to plate a section of a cylinder 60 which is rotated as shownby the arrow into plating electrolyte 61 so that the entire surface ofcylinder 60 can be plated. This type of operation could be performed bya continuous belt of activator material but, as is pointed out below,the present structure even here has some distinct advantages over thebelt approach. Here the flexible outboard support members are shown at62 being driven over pulleys 63 by suitable drive means (not shown). Aplurality of flaps 64 of activator material are positioned over andlocked between the cross-connecting pins 62' and are pulled through aplating zone defined by the surface of cylinder 60 and a perforated,plastic pressure plate 65 having a plurality of openings or perforations66 therethrough to permit the electrolyte 61 to readily flow into suchplating zone. Beneath and adjacent the pressure plate 65 are a pluralityof soluble anode bars 67 supported on rack 68. Cathode contactor 69 isshown riding against the surface of the rotating roll 60. As shown inthis view, the flaps 64 hang loosely from the cross-connecting pins 62'except where they move into and are confined by the walls of the platingzone, i.e. by the surface of roll 60 and the upper face of conformingpressure plate 65. The gap of the plating zone is set so as to slightlycompress the material of the flaps 64. This will give a pressure ofbetween about 0.01 to 0.3 pound/in. depending upon the specificconstruction of the activator material used. This pressure range appearssatisfactory for N-E-T I plating of most metals. Hard chrome cantolerate much higher pressures without producing undesirable propertiesin the deposited metal or any significant wearing away of the plate.Speeds of movement of the flaps across the surface to be plated willgenerally range from about surface feet/minute up to about 1000 surfacefeet/minute with usual speeds in the range of 200 to 400 surfacefeet/minute. Rotation of the cylinder 60 counter to direction of travelof the flaps 64 (as illustrated) permits obtaining this relative motionwithout excessive speed requirement of the flap units 64, e.g. thecylinder can be rotated at several hundred surface feet per minuteitself.

Apparatus of the type herein described and claimed possesses a number ofadvantages over the belt units illustrated in some of the aforementionedpatents. It not only can be used for convolute surfaces which a beltcould not cover or could cover only with very complex drive mechanisms,but it permits of replacement of sections in the event of undue wear atany point whereas a belt must be completely replaced if a portion of itfails. Further, closer gap settings can be maintained. Since all drivemembers are outside of the plating zone defined by the gap. An extremelyimportant feature of this construction is that the width of theactivator material is limited only by the needed rigidity of thecross-connecting members. Belts are generally limited by the need tomaintain dimensional stability to width not much in excess of 12 to 24inches. The present apparatus can be used with flaps up to 30 inches ormore in width and it is ideally constructed for plating contours such asthe epi-trochoid illustrated in FIGS. 4 and 5, ovals, U-shapedinteriors, etc. While it is preferred to run the activator flapssubmerged as illustrated in the drawings, the units can be operated withelectrolyte sprays fed into a non-submerged plating zone should it benecessary or desirable for some reason. Several variations of supportingstructures are shown and obviously a number of other constructions canbe used in place of those illusstrated. Drives can be by tension overdrive pulleys only such as for structures illustrated in FIG. 1 or bypositive engagement of the supporting structure with drive pulleyshaying geared or toothed surfaces, e.g. the structure of the supportmeans illustrated in FIG. 3.

I claim:

1. In an electrodeposition apparatus adapted to have an anode, cathodeand liquid electrolyte present in the plating zone, the combinationcomprising:

(a) means to position in a fixed location a contoured cathodicworkpiece;

(b) a conforming, perforated pressure member closely spaced from saidcontoured workpiece and defining an open plating zone therebetween;

(c) driven supporting means parallel to and outboard from saidso-defined open plating zone; and

(d) a plurality of hard particle supporting means affixed to and movedby said driven supporting means through said open plating zone incontact with said contoured workpiece and said pressure member withinsaid plating zone.

2. Apparatus as in claim 1 wherein said conforming pressure member is aninert anode.

3. Apparatus as in claim 1 wherein said driven supporting meanscomprises a pair of parallel, flexible, spaced members.

4. Apparatus as in claim 3 wherein a plurality of cross members areafiixed to and interconnect said parallel, flexible, spaced members.

5. Apparatus as in claim 1 wherein said hard particle supporting meanscomprise porous, open, resilient webs having a plurality of spaced hardparticles aflixed to at least the outer surface thereof,

6. Apparatus as in claim 5 wherein a plurality of rigid members affixedto said driven supporting means engage, support and move said webscarrying said hard particles as a plurality of flaps folded over each ofsaid rigid members.

7. Electrodeposition apparatus comprising:

(a) a plating tank adapted to contain a liquid electrolyte;

(b) means to fix a workpiece having a two-dimensionally contouredsurface to be plated within said tank;

(c) a pair of flexible supporting members adapted to be positioned insaid tank adjacent each side of said workpiece and extending parallelwith said contoured surface thereof;

(d) a plurality of flexible flaps of hard particle-carrying materialafiixed to and suspended between said flexible supporting members;

(e) means to move said flexible supporting members so as to contact saidcontoured surface with said hard particles on said flexible flaps;

(f) means to apply pressure to said flexible flaps as they pass over andin contact with said contoured surface; and

(g) means to apply an electrodeposition potential whereby said contouredsurface receives electrodeposited metal ions while said flaps arepassing thereover and in contact therewith.

8. Apparatus as in claim 7 wherein said means to apply pressure is aperforated anode.

9. Apparatus as in claim 7 wherein said hard particlecarrying materialis a porous, resilient and fibrous Web.

10. Apparatus as in claim 7 wherein said workpiece is an engine housinghaving interior contoured surfaces to be plated, such surfaces definingan epi-trochoid shape.

References Cited UNITED STATES PATENTS 3,723,283 3/1973 Johnson et al.204-224 R X 936,472 10/1909 Pfanhauser 204Dig. 10 3,661,752 5/1972Capper et al. 204Dig. 10

TA-HSUNG TUNG, Primary Examiner D. R. VALENTINE, Assistant Examiner US.Cl. X.R. 204-227, DIG. 10

